『Sterile Insect Technique』のカバーアート

Sterile Insect Technique

Sterile Insect Technique

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 This week we talk about flesh-eating screwworms, weeds, and the US cattle industry.We also discuss genetic modification, procreation, and tsetse flies.Recommended Book: 1177 BC by Eric H ClineTranscriptThe term ‘autocidal control‘ refers to a collection of techniques that are meant to control populations of some type of living thing, animal or plant, by disrupting their procreationary capacity.So rather than attempting to control pest by spraying poisons all over the place, or controlling plants you consider to be invasive weeds by launching huge weed-pulling efforts in the afflicted areas, you might instead figure out how to keep this current generation of pests and weeds from having as many offspring as they might otherwise have, and then repeat the process with the next generation, and the next, and so on, until the unwanted species is either eradicated in the relevant region, or reduced to such a small number that its presence is no longer such a big deal.There are all kinds of approaches one might take in trying to achieve this sort of outcome.Experimental genetic modification measures, for instance, have been tried in, so far at least, limited ways, the idea being to either make the disliked species less competitive in some way (by making them slower, and thus more likely to be eaten by predators, maybe), or by making them less likely to have offspring, or less likely to have fit offspring—the next generation becomes super slow and clumsy, or they’re carriers of a gene that keeps them from procreating as much, or at all.That approach seems like it could be effective, and there are quite a few efforts, globally, that’re working to refine and perfect it with mosquito species in particular, specifically the ones that are carriers of malaria-causing parasites and similar maladies that cause immense harm to local human (and other mammal) populations.There have also been attempts to spray mating grounds with pheromones that disrupt mating behavior, or to use what’s called the Autodissemination Augmented by Males, or ADAM approach, which has been used to decent effect in some trials, and which involves basically just sprinkling a bunch of male mosquitos with pesticide, releasing them into mosquito mating grounds, and then having them deliver those pesticides to the females they mate with.All of these efforts are meant to reduce populations via some procreationary mechanism, while also attempting to ameliorate some of the other issues associated with other, widely used pest- and weed-control approaches. Most of which rely on some kind of chemical being introduced into the right environment, that chemical helping to kill or disrupt these populations, but in many cases also leading to unwanted, and often initially unforeseen side effects, like those chemicals messing with other species, getting into the groundwater and possibly being associated with maladies in humans, and so on.What I’d like to talk about today is another approach, the sterile insect technique, why it’s become so popular in recent decades, and how it’s being used, today, to address a burgeoning population of a pest that was previously eliminated in North America using this technique, but which has recently become a problem, once more.—The New World screwworm fly is thus named because its larvae, its baby offspring, are planted in warm-blooded animals. These offspring eat not just dead tissues, like the maggots of other flies, but healthy tissues as well.These maggots are often deposited near wounds, like cuts or scrapes, but also injuries caused by the castration or dehorning of cattle, or orifices and other sensitive areas with soft tissue, like the corner of a host’s eye.They don’t typically infest humans, but it does happen, and they’re most likely to be found on wild and domesticated mammals, the females of the species depositing somewhere between 250 and 500 eggs in the flesh of their hosts, the maggots screwing their way deeper into their host’s flesh as they grow, burrowing and eating for the next three to seven days, at which point they fall off and enter the next stage of their lifecycle. By that point the host may already be dead, depending on the extent of the damage these things manage to cause in the interim.These flies were originally found across the Americas and on some Caribbean islands, and they have long been a headache for cattle ranchers in particular, as they will sometimes infect one cow or goat, and then work their way through the entire herd in relatively short order, causing enough damage to seriously injure or kill a whole lot of the rancher’s stock.As a result, humans have been trying to get rid of these things for ages, but nothing seemed to make much of a dent in their populations until the emergence of what’s called the sterile insect technique, which is exactly what it sounds like: a method of autocidal control that involves sterilizing members of the species, usually the ...
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